Saturday 9 March 2013 02.45 EST
First published on Saturday 9 March 2013 02.45 EST

Like many brides-to-be, I slightly lost my mind. Never have I been so concerned about different shades of off white – or the photographic qualities of slipper satin. My preparation was like a military operation involving facials, manicures, practice makeup sessions, dumb-bells and even the occasional sun bed. (I told you – insane.)

Like a benign dictator, I corralled my entire family into the day's preparations. "It's about everyone," I'd insist, grimacing at myself in the nearest mirror and wondering about getting my teeth whitened.

Yet although I was clearly not completely rational, I did mean that – I wanted it to be a family day. And that obviously meant Dad had a starring role.

He hadn't been diagnosed with anything at that point, but the runup to the wedding coincided with our beginning to have doubts about his health. The day itself was in September 2009, and in the preceding weeks it became increasingly evident that something was awry.

This was when his forgetfulness and untidiness shifted from personality quirks into something else.

So I had to swiftly recalibrate my expectations of the father of the bride. He wouldn't be making a tearjerking yet humorous speech about my finer qualities. Or leading the toasts. Or even indulging in a spot of dad dancing and making everyone laugh.

To be fair, he was always so shy that such things would have been a stretch for him anyway. But now it was clear that if he managed to give me away without incident, that in itself would be an achievement .

So we focused on that. In the rehearsal he just about kept it together, remembering where to sit and his moment to stand up. I kept my fingers crossed, hoping that the familiarity of our venue – the church in the parish where I'd grown up – would help things along.

The day dawned and he arrived at Mum's house, smart in his morning suit, hair combed, but distracted. He parked himself at the kitchen table and tucked into a buck's fizz and bagels while the rest of us rushed around. He enjoyed being caught up in the excitement, but already it was a bit like his reactions were taking place behind a pane of frosted glass.

In the car on the way to church, it was the same. It was just me, my sister Ellie, the driver and Dad. Gliding along Cornish lanes, the sea glinting in the background, was a lovely moment. But Dad was a vacuum in the middle of it. He was as passive as a child. Not once did he look me in the eyes, or squeeze my hand and reassure me.

I don't want to sound self-pitying. Given how swiftly he's deteriorated since then, I know how lucky I was to have him play a role at all. But looking back, some fundamental bit was missing, even if the rest of the world couldn't see it yet. Outside the church, we had a moment together.

I've got a picture of it – me staring gravely at Dad and he looking back to me. It looks for all the world like the tender father-daughter exchange I had wanted. But what you can't see is just how far away Dad's eyes were. Yet his behaviour was faultless at the ceremony. He walked me down the aisle calmly and took his seat. At the reception, he sat by my side nursing a champagne flute while my mother gave a speech in his stead, his eyes welling up at all the right moments.

Later, I remember how much he laughed as the evening went on. He might not have been fully who he had been, but I'm so glad he was there.